Andricus pattersonae
Bisexual generation
[Photos of this gall appear on page 12 of the pdf]
On the margins of young leaves, occasionally submarginally, more frequently on the basal section of the leaf, rarely on the leaf stem; more commonly on the lower leaves of small trees. Individual galls about 3x1 mm, eccentrically fusiform-ellipsoidal, apex attenuated and curved; the surface densely micro-spinose. Immature galls pale green, maturing to dark red. Single monothalamous, but sometimes in groups of 2-4, possibly 8 or 9 on a leaf. Emergence hole is at the upper end of the gall, below the apex. Parasitized galls are often more globular and variable in size, usually brighter red.
Range: west-central CA
Adults of the bisexual generation emerge during late May to early June, and females oviposit on the undersides of leaves. Galls that are too crowded develop at an uneven rate and many do not mature. The agamic females may emerge the following spring, late March to early April; however, a diapause within the gall for 1 or 2 years is common.
”- David Evans: (1972) Alternate generations of gall cynipids (Hymenoptera: Cynipidae) on Garry oak©